It all comes down to safety and the law.

There seems little ambiguity as to why Sir Bob Jones was evicted from an Air New Zealand flight yesterday.

The property investor was seated next to an emergency exit, which requires passengers to pay attention to specific crew instructions.

When he refused to listen and wouldn't move, the captain became involved.

Civil aviation lawyer Angela Beazer explains the law is clear cut.

"If a passenger has agreed to be seated there and then isn't willing to listen to the safety briefing the airline and pilot in command might consider that that constitutes some sort of risk."

Angela Beazer says passengers sign up to those terms of carriage when they buy a ticket.

A spokesman for the CAA points out the incident is a reminder to passengers that it's critical they pay attention to all instructions given by the crew, even if they are familiar with the routine.